Self-adjusting hydraulic brake actuator



June 27', 1950 F. M. FIKE SELFADJUSTING HYDRAULIC BRAKE ACTUATOR Filed Jan. 21, 1947 2 Sheets-Sheet 1 FIG. 3.

I game/MM FLOYD M. FIKE,

Patented June 27, 1950 UNITED STATES OEFiFl CSE SELF-ADJUSTING nymmmslo-isnme FAGTUATO'R .Floyd -:M. Fike, Flagstafi, .Ariz.

"Application JanuaryZl, 1947, Serial No. 723,324

- Ih'e object ofmy'-inventionis to providea selfadjusting hydraulic brakeactuator whichis a'selfadjusting and adapted to maintain automatically a =p'rede'termined clearance between the brake shoes and the drum regardless of wearor expansions and contractions o'f -the brake zdrumicaused by heat variations.

-"Another object of my invention is to viprovide a hydraulic brake actuator havingmeans zfor trapping a predetermined amount of liquidfto serve as =':a s'topto release movement-of'tthe brake actuator,-sa-id means leeing automatically adjustable todetermine the :volume 10f :the liquid :50 trapped to define thefidesire'd release clearance.

A "further object Of: my 4 invention is '.to .provide a self-adj usting hydraulic brake actuator having a new and improved means for adjusting the brake release clearance, affordingianwxtensive wear range 'limited only'by the maximum extent of movement of thebrake cylinderzpiston -and adapted to' effect minutely graduatedi adjustments to compensate ior wear or -drum expansions caused lay-heatcreated -by continuous .use of the brakes.

-'A-=still-further objectof -my inventlon .iscto provide-a hydraulic brakeactuator-equippedswith means ---for releasing-=excessive pressure which might cause an over-adjustment 1 due to drum contractions following "drumexpansions :caused by heat.

*A still further objectf -myflinvention provide a hydraulic -bra-ke actuator lre'quiring no more space than theactuatorsused heretofore,-and--'su'ch-that it can be installed in existing automobileand truck brake cylinders as -Well.=as in't-hose 'designed for its use.

Another object of my'inventionis taprovideua hydraulic brake actuator adapted to be =use'cl eon cars, trucks, airplanes, tractors, or any other moving vehicle equipped with hydraulicsbrake means.

Other obj ectsof my invention may appeariin the followingspecification 'descri-bing-Lmy invention-with' reference to the accompanyingsdrawings illustrating-a preferred embodiment or my invention.

Itis, however; to be 'understood that myuinvention is' notlimited-or restricted tethe -exact construction and combination "of par-ts =described:: in

is ito.

made which fall within the :scop of .the cl-aims appendedhereto.

:In :the JdIEWin-gSZ Figure ,1;is;a:longitudinalsectional view taken on the vertical l-longitudinal .centergplane 10f a hydraulic 7 brakaactuator according. totmyinvention.

:iiigure 2 .a transverse sectional view taken on. lined- 2 ofrFigure 1.

Figuree3--isra;perspective view of a. stopring usedzi-ns connection :with my invention.

.rEigure .14 -.is -.a :side -elevational view of a valve body. v

Figure-.5 is :a longitudinal sectional view-of a modified form 0f the brake actuator, the ,view

being taken on lined-e5 iofFigure- 6.

Eigure 6 is: a ,fragmentary elevat ion a1 view of; aibrakerequipped .iwith-a brake; actuator accordinglto myzinvention.

figure "7 a longitudinal ,sectional "view of another modified 'g-iorrn of the bralgeactuator accordingtmmy invention.

\Referrin'g :now' 1113 detail to the drawings, the hydraulic tbrake actuator, forming the subject matter; of :my invention comprises asstepped bore cylinder 40. ;,!Ihe (cylinder can, :however, be. a straight -,bor.e cylinder, as .shown: in Figure; 5, ,(or it:can be :of; the closedend type, asshown in .Figure 7, it being understood thata closed-end cylinderLQperates onlyl'onerbrake. shoe, while a doubleendrcylinder operates-two brake shQ s.

.Aszshown in Figure; 1, the circumferential wall of thezcylinder ll)hasintermediate the ends-of said cylinder 1a qdiametrically, extending hole .or port" H having-a tapped counterbore l2- to which, a brake (not shown) is adapted to be connected. :Althouglr the stepped cylinder :endsare ofdifferent internaladiameter, tthe arrangement of the parts :in ithe 'ytwo ;cy1in=der ends symmetrical about the;diam-etrical center plane of the cylinder. Each cylindereend hastherein-at-the axially inwardrend-zthereof-rand at thecorresponding side of saidudiametrical plane a ret ainer rdisk l3; hav- 'mgaanroutside :diameter. smaller than the, inside diameter; :ofthe related cylinder tend. ,Eacirretamer: disk -.l-3 i'has anjcentral axially .outwardly extending hollow boss- Hi, provided with, an-axial round hole: 1:5; surrounded. by an-axial-lyoutwardly extending'valve seat I56.

zPositi'onedsin each cylinder vend axially .outwardly liof cits: retainer =disk 13 ,is :a cylindrical valyep'tbddy t7. Withinxamaxial cylindrical opening in -the valve cbody 1 closed at'. its .outward.- end, is a slidable'cupshaped release. pistonil 8:.presseid inan axially' inwarddirection 'byia valve "body release spring I9 located between the piston I8 and the closed end of the valve body opening. A rubber cup valve 20 which abuts the closed axially inward end of the cup piston I8 is slidable in the cylindrical opening of the valve body I! and. is arranged to be pressed against the valve seat It by the piston I3 and its spring I9 so as to close the round hole I in the retainer disk I3.

On the axially outward end of the valve body I! is a short cylindrical portion 2I substantially smaller in diameter than the valve body H. The diameter of the valve body I1 is slightly smaller than that of the inside diameter of the related end of the wheel cylinder Ill, and the periphery of the valve body I! is formed with a circumferential groove 22 which defines inner and outer flanges 23 and 24, respectively. p

A metal snap ring 25, secured in a circumferential groove cut in the bore of the cylinder III is arranged so that it is located between the two stop flanges 23 and 24, whereby axial movement of the valve body I! in the cylinder bore is limited to the difference between the thickness of the snap ring 25 and the width of the groove 22 between the stop flanges 23 and 24.

A portion 26 at the axially inward end of the valve body inwardly of the inner stop flange 24 is smaller in diameter than the bottom of the circumferential groove 22, and the portion 25 is traversed by a plurality of circumferentially spaced radial holes 21, which communicate intermediate their ends with longitudinally extending holes 28 formed parallel to the axis of the body I1 and surrounding the short axially outwardly projecting'portion 26 and opening through the axially outward end of the body H.

An axially inwardly projecting annular flange 29 on the valve body portion 26 is registered with the axial cylindrical opening in the valve body I! and an annular outwardly tapered groove 32] surrounds the flange 29. A rubber retaining cup 3| is provided with a center hole surrounded by an inwardly bevelled lip 32 fitting in the groove 30 with the flange 29 of the valve body I'I inv the center hole of the retaining cup. The outside diameter of the retaining cup 3I is the same as that of the retainer disk I3 and the circumferential lip 33 of the retaining cup extends in an axially outward direction.

The hollow boss I4 of the retainer ring I3 is pressed into the axially inward end of the cylindrical opening of the valve body I! so that the axially inward end of the valve body flange 29 abuts the retainer ring I3 and the retaining ring engages the body of the rubber retainer cup 3|, Within its lip 33.

A main helical spring 3 is compressed between the two retainer rings I3 with the opposite ends of the spring positioned in the hollow bosses I4.

Slightly spaced outwardly from the axially outof the springs I 9, so that the fluid can then flow through the holes 21 into the annular space surrounding the valve body, thereby expanding the lips 33 of the cups 3i tightly in the cylinder ends,

-main spring 36 in opposite directions added to the fluid entering the cylinder I0 and acting ward end portion 2I of the valve body I! is a piston cup 35 dovetailed to the inward end of a wheel cylinder piston 36, as indicated at 31.

On one side the wheel cylinder I0 is provided with a bleeder valve construction 38 communicating with the interior of the cylinder for a purpose to be described hereinafter.

When upon application of the brakes, brake fluid under pressure enters the cylinderv II] through the port II, it flows into the space between the retainer rings I3 and into the holes I5 in the bosses I4, where it is stopped by the cup valves 28. If-the pressure is sufficiently high I the rubber cup valves 23 are forced outwardly away from their seats I6 against the resistance against the inner stop ring 24 and adjacent portions of the inward end of the .valve bodies moves the valve bodies in axiall outward directions, until the inner stop ring'2d engages the snap ring 25. Thislimitation' of outward movement of the valve bodies I? determines the brake shoe to drum clearance. Ihe bleeder valve 38 enables venting of air from the cylinder when the brake system is serviced or is being filled with fluid.

When the brakes are released after being applied, the fluid pressure on the inward faces of the retainer rings I3 subsides to'a point at which the valve release springs I9 can return the rubber cup valves 20 into engagement with their seats I5. This traps brake fluid in the cylinder ends between the piston cups 35 and the valve bodies I'l, so that the spacing of the valve bodies and the related piston cups which obtain upon application of the brakes is maintained in the released condition of the brakes until a subsequent application of the brakes, and the brake shoe retracting spring a2 is thereby prevented from retracting the brake shoes M1, and hence the pistons 3%, beyond that amount providing desired clearance between thebrake shoes and the drum.

The above described arrangement of the actuator is such that in the event that the brake drum M contract due to cooling thereof from a, hot expanded condition, wherein clearance between the drum and shoes is eliminated, the actuator automatically adjusts itself to re-establish a proper clearance. This adjustment takes place upon application of the brakes in the absence 'of clearance between the drum and the shoes. As the brakes are so applied, with consequent increasein pressure of the brake fluid in the inlet passagevor hole II, the valve body I'I being unable to move outwardly because of the fluid trapped between said valve body and the piston cup 35 and the piston 36 being unable to move outwardly, the increased pressure overcomes the release springs I9 and moves the rubber valve cups 20 from their seats It. This opens the holes I5 and permits the fluid trapped between the valve bodies I? and the piston cups 35 to escape through the passages 28 and said hole I5 and free the valve bodies Il to be moved outwardly by the main spring 34 until the inner stop flange 24 abuts the snap ring 25. w

Upon release of the brakes after the above described actions the pressure in the inlet port II subsides so that the rubber cup valves 20 are reseated against the valve seats I6 by the release springs I9, whereby the fluid present between the valve bodies IT and the piston cups 35 is trapped again.

As the brakes become fully released, the pressure in the inlet port II is fully relaxed so that the brake shoe return spring 12 can overcome the main spring 34 and cause the valve bodies I! to move inwardly untiltheir outer stop flanges angers {saunas-snap an; wherehy the'bralieshoes snare-r ed fidm tne brake 4-1 whereby a clearance therebeti'veen equal to the ldista'nce flange? manne in Figured a med-heathen of the brake actu a'tor is shown, flfl'iele'n 1r feons'truction of the workingjparts is exactly a's i that "the cylinder 143a of rition'is shown. In 6f the clo'se'd' rid 'erated; 'so that the on nae- 6m delineate-nagbia'ke actuator as de' ribed 'above. I v I v 'I IavingdeScribed my invention, I claim as new anddesi're 1:0 secure by Letters Patent:

-1.--*A hydraulic-brakeacti1ator,'-a' wheel cylinder inga'vnve -bedy including a piston cup istc'in arran'ged to-be' -moved "axially in said anti-(le end piston cupfand" -piston being 'connected togetherto move as""a"unit,'the exterior of said valve body being form'd'with a circumferritial groove defining outward and inward stop flanges, the interior of said cylinder being formed with a circumferential groove, a snap ring positioned iii-said interior groove and projecting into the external groove of said valve-body, said snap ring being narrower than the space between said stop flanges to permit limited axial movement of said valve body in said cylinder.-

2. A h y'idraulic-brakeactuator for a wheel cylinder fcompr'isinga valve body comprising a piston cupand-a'piston adapted to be moved axially in said cylinder, said piston cup and said piston being connected together to move as a unit, said valve"body being provided with a circumferential groove defining outward and inward stop flanges, a snap ring arranged in an inner circumferential groove in said cylinder and extending into the circumferential groove into the valve body between said stop flanges to limit the axial movement of said valve body, said valve body having a cylindrical bore therein closed at its axially outward end, said cup piston being slidably arranged in said bore, a helical spring compressed between the closed endof said bore and said cup piston, a rubber cup valve slidably mounted in said bore and abutting said cup piston, a retainer ring, a perforated hollow boss centrally formed on said ring and secured in the axially inward end of said bore in the valve body, and

a main helical spring engaging said retainer ring in a manner to urge said valve body in an axially outward direction.

3. A hydraulic brake actuator for a wheel cylinder comprising a valve body comprising a piston cup and a piston adapted to be moved axially in said cylinder, said piston cup and said piston being connected together to move as a unit, the said valve body being provided with a circumferential groove defining outward and inward stop flanges, a snap ring arranged in an inner circumferential groove in said cylinder and extending into the circumferential groove in the valve body between said stop flanges to limit the axial movement of said valve body, said valve body having a cylindrical bore therein closed at its axially putward end, said cup piston being slidably between tliepnap nag 2 5 and thie fbiiter stop;

described 'alc'ative, the

a s'tra'i"ghi'ror uniform bore ed form of brake arranged n an eer e, nares; series can:

S mour'itedin said-bore and abuttmg said 'cui l pis 1 tonjaretainer ring,- a 'perforaited hollow b'os's cenhollow mess; the named helical s'prihg" urgmg said rubber 'cup *va'lv'e into engagement with said sea-t, said valve body being traversed "by a plurality of longitudinally extending and-radially extending holes, sa'id" holes Communicating c'ach otlier, and 'a rubber retainer cup :on said eetainer ring, the radially outward "ends of said radial 'holes'bi-n'g located adjacent 'to saiti re- 4. Anydra ic brake aotfiatdr for srwneel bill-'- i-nder comprising a valve body c'oinprising a pist'on cu -and -=a-piston adapted to bemoved axially in said-cylinder;saidpiston cu -and said piston being corine'cted' toge'thr -to' 'rnove as a iinit, the s ai'd vall e body beihg provid d' with a'circumferentia1 roove defining utward and ":inviardstop' flanges, a'sna'p ring 'arra-ng'ed in an inner circumferential groove 'in 's'aid yli'nde'r and extending an to the eir' umfersnzna g-roov'e in the valve body between sa-id Ste'p flae'S td-li lnit ial movementnf said valve- 'haLVi-l5ig a y-Iirrdricalhere the ein'-closed ='at chi-Said (it'll) listdn being SI-idabW arl anged said bd'r'e, -*a' helical spring corn-r3 ssedmetween the 'cl e capee 6f S'ai'd' b dre alld *cup pistdh 24 and abutting s'aibl cup Ipi'ston, 'a retainer-ring,- a generated hollovf'b'osscentrally-farmed on said ring and secured in' the axially i-nwair d end 'o-f said borein the' ve b'odyy'a in h' helic'a'l spring nga'ging said retainer ring in a m i 'e fmi {urge said valve body in an axially outward dii ection, a valve seat' fori'hed on s'aid houowbo-ss; tne nrst named helical spring ur ingsai'd rubber cup v alv'e into engagement with said seat, said valve body being traversed by a plurality of longitudinally extending and radially extending holes, said holes communicating with each other, a rubber retainer cup on said retainer ring, the radially outward ends of said radial holes being located adjacent to the retainer cup, and a bleeder valve traversing the wall of said cylinder and communicating with the interior of said cylinder adjacent to said inward stop flange on said valve body.

5. A self-adjusting brake actuator comprising a wheel cylinder having a pressure brake fluid inlet port, spaced from one end of said cylinder, a brake shoe operating piston in said one end of said cylinder, a centrally apertured retainer disk located in said cylinder between said inlet port and said piston and spaced axially inwardly from said piston, said retainer disk having a valve seat communicating with the central aperture of said retainer disk, a valve body positioned for axial movement in said cylinder between said retainer disk and said piston and upon which said retainer disk is mounted, said valve body being formed with a longitudinal bore aligned with said valve seat and closed at its axially outward end, axially inwardly spring pressed valve means in said bore normally engaging and closing said valve seat, said valve body having a pair of axially spaced peripheral flanges slidably fitting the interior of said cylinder, a projection on the interior of said cylinder projecting into the space be-q sq fsaid nn'g {secured 'i-h the n ard'endofs'aid borein the v'alvebo'dy, amamheiicars'pnng engagingsam-retainer nag tween and being narrowerthan the space between said flanges whereby said valve body is confined to limited axially outward and inward movements, said valve body being formed with longitudinal passage means opening at the radially outward end thereof between said valve body and said piston, said valve body further being formed with radial passage means communicating with the axially inward ends of said longitudinal passage means said radialpassage means Opening at the radially outward end thereof into a space existing betweensaidretainer disk and said axially inward stop flange and defined by a reduced inward portion on said valve body, and a main spring operatively engaging the axially inward side of said retainer disk and urging said valve body in anaxially outward direction.

6. A self-adjusting brake actuator comprising a wheel cylinder having a pressure brake fluid inlet port, spaced from one end of said cylinder, a

brake shoe operating piston insaid one end of said cylinder, a centrally apertured retainer disk located in said cylinder between said inlet port and said piston and spaced axially inwardly from said piston, said retainer disk having a valve seat communicating with the central aperture of said retainer disk, a valve body positioned for axial movement in said cylinder between said retainer disk and said piston and upon which said retainer disk is mounted, said valve body being formed with a longitudinal bore aligned with said valve seat and closed at its axially outward end, axially inwardly spring pressed valve means in said bore normally engaging and closing said valve seat, said valve body having a pair of axially spaced peripheral flanges slidably fitting the interior of said cylinder, a projection on the interior of said cylinder projecting into the space between and being narrower than the space be- 1 loodyand said piston, said valve body further being formed with radial vpassage means communicating with the axially inward ends of said longitudinal passage means, said radial passage means opening at the radially outward end thereof into a space existing between said retainer disk and said axially inward stop flange and defined by a reduced inward portion on said valve body, and a main spring cperatively engaging the axially inward side of said retainer disk and urging said valve body in an axially outward direction, said longitudinal and radial passage means being arranged to pass fluid into the space between said retainer disk and said axially inward stop flange when sufficient fluid pressure is exerted through said inlet port and the central aperture of said retainer plate to augment the pressure of said main spring to unseat said spring pressed valve means from said seat, whereby said brake shoe operating piston is moved in said cylinder in an axially outward direction, relaxation of said pressure permitting said spring pressed valve means to return to and close said valve seat so as to trap fluid present inthe space between said piston and said valve body and in the space between said retainer disk and said axially inward stop flange and therebyprevent axially inward displacement of said valve body and axially inward displacement of said piston.

REFERENCES CITED The following references are of record in th file of this patent: 1

UNITED STATES PATENTS Number Name Date 697,140 Goldschmidt Apr. 8, 1902 2,156,120 La Brie Apr. 25, 1939 2,189,134 Chard Feb. 6, 1940 FOREIGN PATENTS Number Country Date 374,150 Great Britain June 6, 1932 

